1. Field of the Invention
The present invention relates to a packet forwarding apparatus for controlling the bandwidth of a packet flowing on a network for example, and a method thereof.
2. Description of the Related Art
In a packet type communication system employed in an IP network, a large number of users can share the same line, thereby making it possible to reduce the cost per bandwidth. Due to the low cost of the packet type communication system, there are moves to achieve telecommunication networks and business networks of enterprises with IP networks in place of private networks which have heretofore been used. It is required for IP networks to ensure quality of service (QoS) for voice data and mission critical data that have been achieved through private networks and achieve high availability.
In order to ensure the QoS, it is necessary that a packet forwarding apparatus constituting an IP network has a QoS control mechanism for ensuring QoS for voice data and mission critical data. As a QoS control mechanism, there is known a shaping function for example. Japanese Patent Application Laid-Open No. 6-315034 (document 1) describes a shaping apparatus for carrying out the shaping function. The shaping apparatus described in document 1 includes a queue for storing a cell of a fixed-length packet for each virtual connection (VC) and transmits a packet from the queue with a predetermined bandwidth for each VC to ensure a bandwidth for each VC. For example, an administrator of an IP network disposes this shaping apparatus at a port where traffic concentrates and assigns VC to voice data and mission critical data, thereby making it possible to ensure QoS for the data.
As another shaping apparatus, there is known Weighted Fair Queuing (WFQ). A shaping apparatus of WFQ based on an algorithm called Self Clocked Fair Queuing (SCFQ) is described in document 2 (S. Golestani, “Self-Clocked Fair Queuing Scheme for Broadband Applications”, In proc. of INFORCOM' 94, pp. 636-646, 1994.). The shaping apparatus described in document 2 manages a plurality of k's (where k=1 to N) and has weight Wk for each session k. When a packet p_k_i arrives at the shaping apparatus, the shaping apparatus stores the packet p_k_i into a queue and calculates variable F_k_i for each packet p_k_i according to the following equation.F—k—i=L—k—i/Wk+max(F_(k−1)—i,V(ta—k—i))
where, L is a packet length of packet p_k_i, ta_k_i is an arrival time of packet p_k_i, and V(t) is a function that returns a value of F_k_i of a packet outputted at time t. For the output of a packet, packet p_k_i having the minimum F_k_i is outputted, thereby implementing packet output in proportion to weight Wk of each session. For example, the administrator of the IP network assigns one session k to voice data and mission critical data to ensure the bandwidth for Wi/(total sum of Wk)×port bandwidth, thereby making it possible to ensure QoS for the data.
On the other hand, a link aggregation technology for achieving high availability of a packet forwarding apparatus is described in document 3 (Link Aggregation according to IEEE standard 802.3ad (http://www.triumf.ca/canarie/amsterdam-test/References/wp-lag-e.pdf)). According to the link aggregation technology, a plurality of physical ports (physical links) are treated as one logical link aggregation group which can be treated as in the case of one physical port. Even if one physical port of the link aggregation group fails, at least one physical port functions normally; therefore, there is no break in communication between packet forwarding apparatuses connected through the link aggregation group. Accordingly, the administrator of the IP network connects between packet forwarding apparatuses using a plurality of ports to which link aggregation is applied instead of a single port, thus making it possible to enhance network availability.
Further, a fast reroute technology for achieving high availability in a multi protocol label switching (MPLS) network in which a label switching path (LSP) is set is described in document 4 (IETF Internet Draft draft-ietf-mpls-rsvp-lsp-fastreroute-07.txt “Fast Reroute Extensions to RSVP-TE for LSP Tunnels”). This document describes a one-to-one backup method for protecting traffic flowing along an LSP and a facility backup method. According to the document, the one-to-one backup method sets one backup LSP corresponding to a protected LSP, and the facility backup method sets one backup LSP corresponding to a plurality of protected LSPs. When a failure occurs on a protected LSP, traffic flowing along the LSP is detoured along the backup LSP. The administrator of the IP network sets up a backup LSP for a protected LSP to implement the detour, thereby greatly enhancing network availability.